Keep kubernetes secrets if ExternalSecret resource was deleted

[yongzhang]

Hi, team

We found that if ExternalSecret resource was deleted, the kubernetes secret will also be deleted, this is a big risk if we do ack-secret-manager maintenance something like we accidently deleted ExternalSecret CRD which will cause all kubernetes secrets get deleted. Can you consider at least add an option to retain kubernetes secrets if ExternalSecret get deleted?

Ref:
The External Secrets Operator has Retain as the default deletion policy, see this link:
https://external-secrets.io/latest/guides/ownership-deletion-policy/